To start by addressing what my post talked about, no matter how much justifying you do, if the post is in a community where the moderator objects to this behaviour, it will be downvoted or even muted.
Now to address the taking of images through using embedding instead of just straight up stealing.
People who create websites select their assets like images to enhance and draw visitors into their content. Often those assets are also part of their income.
For example, a photographer displaying images of his shots on his site to sell prints and items the image is printed on. You come along and decide one of those images would be great on your article so you link to it and embed it into your article because, well, you think the law says it's okay.
Every time someone visits your article in order for that image to load it does a call from the site where it's being stored.
So, instead of the image being used to promote the photographers work, you're using it to promote your work and stealing the value of the image from the photographer.
To add insult to injury, you're putting more load on the hosting account he's paying for and if his hosting is based on bandwidth, you're increasing the used bandwidth and taking money from his pocket.
Being rude to others is legal too.. I'm trusting you don't teach your students that is okay.